[SQL 문제 풀이] Customer Placing the Largest Number of Orders (가장 많은 주문을 하는 고객)

Jun 04, 2025

[SQL 문제 풀이] Customer Placing the Largest Number of Orders (가장 많은 주문을 하는 고객)

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Customer Placing the Largest Number of Orders - LeetCode

Can you solve this real interview question? Customer Placing the Largest Number of Orders - Table: Orders +-----------------+----------+ | Column Name | Type | +-----------------+----------+ | order_number | int | | customer_number | int | +-----------------+----------+ order_number is the primary key (column with unique values) for this table. This table contains information about the order ID and the customer ID. Write a solution to find the customer_number for the customer who has placed the largest number of orders. The test cases are generated so that exactly one customer will have placed more orders than any other customer. The result format is in the following example. Example 1: Input: Orders table: +--------------+-----------------+ | order_number | customer_number | +--------------+-----------------+ | 1 | 1 | | 2 | 2 | | 3 | 3 | | 4 | 3 | +--------------+-----------------+ Output: +-----------------+ | customer_number | +-----------------+ | 3 | +-----------------+ Explanation: The customer with number 3 has two orders, which is greater than either customer 1 or 2 because each of them only has one order. So the result is customer_number 3. Follow up: What if more than one customer has the largest number of orders, can you find all the customer_number in this case?

https://leetcode.com/problems/customer-placing-the-largest-number-of-orders/description/


가장 많은 주문을 한 고객을 위해 customer_number를 찾기 위한 솔루션을 작성하세요.

테스트 케이스는 한 고객이 다른 고객보다 더 많은 주문을 할 수 있도록 생성됩니다.

내가 작성한 쿼리

Oracle


SELECT customer_number
FROM (
    SELECT
        customer_number,
        COUNT(*) AS count
    FROM Orders
    GROUP BY customer_number
    ORDER BY count DESC
)
WHERE ROWNUM = 1;

MySQL


SELECT customer_number
FROM orders
GROUP BY customer_number
ORDER BY COUNT(*) DESC
LIMIT 1;

차이점

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내가 작성한 쿼리